The Boeing 787 Dreamliner™ airplane has two high bypass turbofan engines, one under each wing. The engines are very large. Each engine has a length of about 160 inches and a fan diameter of about 110 inches.
The engines are mounted to pylons on the wings. During installation of an engine, the engine is moved toward a pylon and maneuvered so mounting holes in its mounts are aligned with mounting holes in the pylon. With the mounting holes aligned, shear pins are engaged in the engine mounts. Once the shear pins are at full engagement, the engine is moved into its final position and fastened to the pylon with tension bolts.
Maneuvering the engine with respect to the pylon is challenging, especially while lining up the mounting holes for the shear pins. Because the engine is so large and because the mounting holes are at the top of the engine, visual sight lines to the mounting holes are poor.